Interstitial lung disease: is interstitial lung disease the same as scleroderma lung disease?

p53 and Myofibroblast Apoptosis in Organ Fibrosis

Organ fibrosis represents a dysregulated, maladaptive wound repair response that results in progressive disruption of normal tissue architecture leading to detrimental deterioration in physiological function, and significant morbidity/mortality. Fibrosis is thought to contribute to nearly 50% of all deaths in the Western world with current treatment modalities effective in slowing disease progression but not effective in restoring organ function or reversing fibrotic changes. When physiological wound repair is complete, myofibroblasts are programmed to undergo cell death and self-clearance, however, in fibrosis there is a characteristic absence of myofibroblast apoptosis. It has been shown that in fibrosis, myofibroblasts adopt an apoptotic-resistant, highly proliferative phenotype leading to persistent myofibroblast activation and perpetuation of the fibrotic disease process. Recently, this pathological adaptation has been linked to dysregulated expression of tumour suppressor gene p53. In this review, we discuss p53 dysregulation and apoptotic failure in myofibroblasts and demonstrate its consistent link to fibrotic disease development in all types of organ fibrosis. An enhanced understanding of the role of p53 dysregulation and myofibroblast apoptosis may aid in future novel therapeutic and/or diagnostic strategies in organ fibrosis.

Regulating Lymphatic Vasculature in Fibrosis: Understanding the Biology to Improve the Modeling

Fibrosis occurs in many chronic diseases with lymphatic vascular insufficiency (e.g., kidney disease, tumors, and lymphedema). New lymphatic capillary growth can be triggered by fibrosis-related tissue stiffening and soluble factors, but questions remain for how related biomechanical, biophysical, and biochemical cues affect lymphatic vascular growth and function. The current preclinical standard for studying lymphatics is animal modeling, but in vitro and in vivo outcomes often do not align. In vitro models can also be limited in their ability to separate vascular growth and function as individual outcomes, and fibrosis is not traditionally included in model design. Tissue engineering provides an opportunity to address in vitro limitations and mimic microenvironmental features that impact lymphatic vasculature. This review discusses fibrosis-related lymphatic vascular growth and function in disease and the current state of in vitro lymphatic vascular models while highlighting relevant knowledge gaps. Additional insights into the future of in vitro lymphatic vascular models demonstrate how prioritizing fibrosis alongside lymphatics will help capture the complexity and dynamics of lymphatics in disease. Overall, this review aims to emphasize that an advanced understanding of lymphatics within a fibrotic disease-enabled through more accurate preclinical modeling-will significantly impact therapeutic development toward restoring lymphatic vessel growth and function in patients.

Periostin overexpression in scleroderma cardiac tissue and its utility as a marker for disease complications

OBJECTIVE

To evaluate the levels of periostin in patients with systemic sclerosis (SSc) and their association with features of systemic sclerosis.

METHODS

The levels of periostin were assessed in the serum of 106 SSc patients and 22 healthy controls and by immunofluorescence staining in cardiac tissue from 4 SSc patients and 4 controls. Serum periostin was measured via enzyme-linked immunosorbent assay. The results were analyzed using Mann-Whitney test or Kruskal-Wallis test followed by Dunn's multiple comparisons tests and Spearman's test for correlations. Cardiac tissue from SSc patients and controls was stained for periostin and co-stained for periostin and collagen type I using immunofluorescence.

RESULTS

Periostin levels were higher in patients with SSc compared to controls and directly correlated to modified Rodnan skin score and echocardiography parameters of left ventricular measurements. Immunofluorescence staining in SSc cardiac tissue showed patchy periostin expression in all SSc patients, but not in controls. Furthermore, there was extensive periostin expression even in areas without collagen deposition, while all established fibrotic areas showed colocalization of collagen and periostin. There was no association between periostin levels and interstitial lung disease, pulmonary hypertension or other vascular complications.

CONCLUSION

Periostin is elevated in SSc cardiac tissue in vivo and circulating levels of periostin are increased in SSc, correlating with the extent of disease duration, degree of skin fibrosis, and left ventricular structural assessments. Periostin may be a potential biomarker that can provide further pathogenic insight into cardiac fibrosis in SSc.

Vaccination-based immunotherapy to target profibrotic cells in liver and lung

Fibrosis is the final path of nearly every form of chronic disease, regardless of the pathogenesis. Upon chronic injury, activated, fibrogenic fibroblasts deposit excess extracellular matrix, and severe tissue fibrosis can occur in virtually any organ. However, antifibrotic therapies that target fibrogenic cells, while sparing homeostatic fibroblasts in healthy tissues, are limited. We tested whether specific immunization against endogenous proteins, strongly expressed in fibrogenic cells but highly restricted in quiescent fibroblasts, can elicit an antigen-specific cytotoxic T cell response to ameliorate organ fibrosis. In silico epitope prediction revealed that activation of the genes Adam12 and Gli1 in profibrotic cells and the resulting "self-peptides" can be exploited for T cell vaccines to ablate fibrogenic cells. We demonstrate the efficacy of a vaccination approach to mount CD8⁺ T cell responses that reduce fibroblasts and fibrosis in the liver and lungs in mice. These results provide proof of principle for vaccination-based immunotherapies to treat fibrosis.

The rationale for targeting the JAK/STAT pathway in scleroderma-associated interstitial lung disease

The etiopathogenesis of systemic sclerosis (SSc)-associated interstitial lung disease (ILD) is still debated and no therapeutic options have proved fully effective to date. The intracellular Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway is highly conserved among either immune or nonimmune cells and involved in inflammation and fibrosis. Evidence from preclinical studies shows that the JAK/STAT signaling cascade has a crucial role in the differentiation of autoreactive cells as well as in the extracellular matrix remodeling that occurs in SSc. Therefore, it is likely that the use of oral small molecule JAK-inhibitors, especially if prescribed early, may prevent or slow the progression of SSc-associated ILD, but few clinical studies currently support this hypothesis.

Regulatory T cells are a double-edged sword in pulmonary fibrosis

Pulmonary fibrosis (PF) is a chronic progressive interstitial lung disease. The pathogenesis of PF has not been clearly elucidated, and there is no obvious effective treatment to arrest the progression of PF to date. A long-term chronic inflammatory response and inappropriate repair process after lung injury are important causes and pathological processes of PF. As an influential type of the body's immune cells, regulatory T cells (Tregs) play an irreplaceable role in inhibiting the inflammatory response and promoting the repair of lung tissue. However, the exact roles of Tregs in the process of PF have not been clearly established, and the available literature concerning the roles of Tregs in PF are contradictory. First, Tregs can advance the progression of pulmonary fibrosis by secreting platelet-derived growth factor (PDGF), transforming growth factor-β (TGF-β) and other related factors, promoting epithelial-mesenchymal transition (EMT) and affecting the Th1 and Th2 balance, etc. Second, Tregs can inhibit PF by promoting the repair of epithelial cell damage, inhibiting the accumulation of fibroblasts, and strongly inhibiting the production and function of other related pro-inflammatory factors and pro-inflammatory cells. Accordingly, in this review, we focus on the multiple roles of Tregs in different models and different pulmonary fibrosis phases, thereby providing theoretical support for a better understanding of the multiple roles of these cells in PF and a theoretical basis for identifying targets for PF therapy.

Estimation of Endostatin level in pulmonary arterial hypertension patients and its relation with some parameters

Biomarkers are attractive non-invasive tools for estimating and monitoring pulmonary arterial hypertension (PAH) disease and for predicting survival in patients with PAH; therefore, many studies encouraged the investigation of new biomarkers to facilitate the diagnosis of PAH. Endostatin (ES) is an endogenous inhibitor of angiogenesis. It is produced by proteolytic cleavage of the collagen XVIII that is present in both normal and cancerous tissue. In vitro examination shows that ES can manage endothelial cells (EC) physiology in ways that could influence angiogenesis. For example, solvent ES hinders EC movement and prompts improvements of the cytoskeleton that incorporate the loss of Actin stretch strands and central grips. This effect embraces restrictions on the α5β1integrins, Tropomyosin, and putative heparan sulfate proteoglycans. Consequences for the human EC cytoskeleton include Es-induced down-regulation of Mitogen-actuated Protein Kinase (MAPK), Focal Adhesion Kinase (FAK), the Urokinase Plasminogen Activator (uPA) System, and the RhoA GTPase. Human ES has likewise been shown in a few investigations to repress EC multiplication. Moreover, ES-instigated cell cycle capture in the G1 stage is joined by Cyclin D1 down-regulation. Of note, ES blocks the proliferation and organization of endothelial cells into new blood vessels, and in animal studies, ES also inhibits angiogenesis and the growth of both primary tumors and secondary metastasis. ES was initially identified by its capacity to inhibit tumor angiogenesis in vitro and also in vivo. It can also be found in both healthy and patient’ serum, and has been detected in peripheral circulation. ES could be an attractive, non-invasive prognostic marker for some diseases, notably PAH. Therefore, the presented work is aimed at investigating the ES level in blood serum as a biomarker for detection, diagnosis and early treatment of PAH patients. In doing so, the association is ascertained between gender, age, body mass index (BMI), waist circumferences, smoking, types of PAH (primary and secondary) and this potential biomarker is assessed in PAH patients.

Resolution of organ fibrosis

Fibrosis is the excessive accumulation of extracellular matrix that often occurs as a wound healing response to repeated or chronic tissue injury, and may lead to the disruption of organ architecture and loss of function. Although fibrosis was previously thought to be irreversible, recent evidence indicates that certain circumstances permit the resolution of fibrosis when the underlying causes of injury are eradicated. The mechanism of fibrosis resolution encompasses degradation of the fibrotic extracellular matrix as well as elimination of fibrogenic myofibroblasts through their adaptation of various cell fates, including apoptosis, senescence, dedifferentiation, and reprogramming. In this Review, we discuss the present knowledge and gaps in our understanding of how matrix degradation is regulated and how myofibroblast cell fates can be manipulated, areas that may identify potential therapeutic approaches for fibrosis.

Predictors of lung function decline in scleroderma-related interstitial lung disease based on high-resolution computed tomography: implications for cohort enrichment in systemic sclerosis-associated interstitial lung disease trials

BACKGROUND

The extent of lung involvement visualized by high-resolution computed tomography (HRCT) is a predictor of decline in forced vital capacity (FVC) in scleroderma-interstitial lung disease. Our objective was to evaluate the performance of three different HRCT-defined staging systems in the Scleroderma Lung Study I (SLS I) over a 1-year period.

METHODS

We assessed two visual semiquantitative scores: the maximum fibrosis score (MaxFib, the fibrosis score in the zone of maximal lung involvement) and visual assessment of total lung involvement (TLI) as proposed by Goh and Wells. In addition, we evaluated the computer-aided diagnosis and calculated the quantitative percentage with fibrosis (QLF) and TLI.

RESULTS

The mean duration of the disease was 3.2 years, and the mean FVC was 67.7 %. Regardless of the staging system used, a greater degree of fibrosis/TLI on HRCT scans was associated with a greater decline in FVC in the placebo group. Using the MaxFib and QLF, the mean absolute changes in FVC from baseline were 0.1% and -1.4%, respectively, in <25% lung involvement vs. a change of -6.2% and -6.9%, respectively, with >25% involvement (negative score denotes worsening in FVC). Conversely, cyclophosphamide was able to stabilize decline in FVC in subjects with greater degree of involvement detected by HRCT. Using the visual MaxFib and QLF, the mean absolute improvements in FVC were 1.2 and 1.1, respectively, with >25% involvement.

CONCLUSIONS

HRCT-defined lung involvement was a predictor of decline in FVC in SLS I. The choice of staging system for cohort enrichment in a clinical trial depends on feasibility.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00004563 (Scleroderma Lung Study I) ISRCTN15982171. Registered 19 Aug 2015.

Redox-fibrosis: Impact of TGFβ1 on ROS generators, mediators and functional consequences

Fibrosis is one of the most prevalent features of age-related diseases like obesity, diabetes, non-alcoholic fatty liver disease, chronic kidney disease, or cardiomyopathy and affects millions of people in all countries. Although the understanding about the pathophysiology of fibrosis has improved a lot during the recent years, a number of mechanisms still remain unknown. Although TGF-β1 signaling, loss of metabolic homeostasis and chronic low-grade inflammation appear to play important roles in the pathogenesis of fibrosis, recent evidence indicates that oxidative stress and the antioxidant system may also be crucial for fibrosis development and persistence. These findings point to a concept of a redox-fibrosis where the cellular oxidant and antioxidant system could be potential therapeutic targets. The current review aims to summarize the existing links between TGF-β1 signaling, generation and action of reactive oxygen species, expression of antioxidative enzymes, and functional consequences including epigenetic redox-mediated responses during fibrosis.

Associations between circulating endostatin levels and vascular organ damage in systemic sclerosis and mixed connective tissue disease: an observational study

Introduction

Systemic sclerosis (SSc) and mixed connective tissue disease (MCTD) are chronic immune-mediated disorders complicated by vascular organ damage. The aim of this study was to examine the serum levels of the markers of neoangiogenesis: endostatin and vascular endothelial growth factor (VEGF), in our unselected cohorts of SSc and MCTD.

Methods

Sera of SSc patients (N = 298) and MCTD patients (N = 162) from two longitudinal Norwegian cohorts were included. Blood donors were included as controls (N = 100). Circulating VEGF and endostatin were analyzed by enzyme immunoassay.

Results

Mean endostatin levels were increased in SSc patients 93.7 (37) ng/ml (P < .001) and MCTD patients 83.2 (25) ng/ml (P < .001) compared to controls 65.1 (12) ng/ml. Median VEGF levels were elevated in SSc patients 209.0 (202) pg/ml compared to MCTD patients 181.3 (175) pg/ml (P = .017) and controls 150.0 (145) pg/ml (P < .001). Multivariable analysis of SSc subsets showed that pulmonary arterial hypertension (coefficient 15.7, 95 % CI: 2.2–29.2, P = .023) and scleroderma renal crisis (coefficient 77.6, 95 % CI: 59.3–100.0, P < .001) were associated with elevated endostatin levels. Multivariable analyses of MCTD subsets showed that digital ulcers were associated with elevated endostatin levels (coefficient 10.5, 95 % CI: 3.2–17.8, P = .005). The risk of death increased by 1.6 per SD endostatin increase (95 % CI: 1.2–2.1, P = .001) in the SSc cohort and by 1.6 per SD endostatin increase (95 % CI: 1.0–2.4, P = .041) in the MCTD cohort after adjustments to known risk factors.

Conclusions

Endostatin levels were elevated in patients with SSc and MCTD, particularly SSc patients with pulmonary arterial hypertension and scleroderma renal crisis, and MCTD patients with digital ulcers. Elevated endostatin levels were also associated with increased all-cause mortality during follow-up in both groups of patients. We propose that endostatin might indicate the degree of vascular injury in SSc and MCTD patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0756-5) contains supplementary material, which is available to authorized users.

Flow Cytometric Identification of Fibrocytes in the Human Circulation

Because the incidence of organ fibrosis increases with age, various fibrosing disorders are projected to account for significant increases in morbidity, mortality, and healthcare costs in the years to come. Treatments for these diseases are scarce and better understanding of the immunopathogenesis of fibrosis and its relationship to aging are sorely needed. One area of interest in this field is the role that fibrocytes might play in the development of tissue remodeling and fibrosis. Fibrocytes are mesenchymal progenitor cells presumed to be of monocyte origin that possess the tissue remodeling properties of tissue resident fibroblasts such as extracellular matrix production and α-SMA-related contractile properties, as well as the immunologic functions typically attributed to macrophages including production of cytokines and chemokines, antigen presentation, regulation of leukocyte trafficking, and modulation of angiogenesis. Fibrocytes could participate in the development of age-related fibrosing disorders through any or all of these functions. This chapter presents methods that have been developed for the study of circulating human fibrocytes. Protocols for the quantification of fibrocytes in the human circulation will be presented along with discussion of the technical challenges that are frequently encountered in this field. It is hoped that this information will facilitate further investigation of the relationship between fibrocytes, aging, and fibrosis, and perhaps uncover new areas of study in these difficult-to-treat and deadly diseases.

Fibroblasts in fibrosis: novel roles and mediators

Fibroblasts are the most common cell type of the connective tissues found throughout the body and the principal source of the extensive extracellular matrix (ECM) characteristic of these tissues. They are also the central mediators of the pathological fibrotic accumulation of ECM and the cellular proliferation and differentiation that occurs in response to prolonged tissue injury and chronic inflammation. The transformation of the fibroblast cell lineage involves classical developmental signaling programs and includes a surprisingly diverse range of precursor cell types—most notably, myofibroblasts that are the apex of the fibrotic phenotype. Myofibroblasts display exaggerated ECM production; constitutively secrete and are hypersensitive to chemical signals such as cytokines, chemokines, and growth factors; and are endowed with a contractile apparatus allowing them to manipulate the ECM fibers physically to close open wounds. In addition to ECM production, fibroblasts have multiple concomitant biological roles, such as in wound healing, inflammation, and angiogenesis, which are each interwoven with the process of fibrosis. We now recognize many common fibroblast-related features across various physiological and pathological protracted processes. Indeed, a new appreciation has emerged for the role of non-cancerous fibroblast interactions with tumors in cancer progression. Although the predominant current clinical treatments of fibrosis involve non-specific immunosuppressive and anti-proliferative drugs, a variety of potential therapies under investigation specifically target fibroblast biology.

CD4+CD25+FoxP3+ Regulatory Tregs inhibit fibrocyte recruitment and fibrosis via suppression of FGF-9 production in the TGF-β1 exposed murine lung

Pulmonary fibrosis is a difficult to treat, often fatal disease whose pathogenesis involves dysregulated TGF-β1 signaling. CD4+CD25+FoxP3+ Regulatory T cells (“Tregs”) exert important effects on host tolerance and arise from naïve CD4+ lymphocytes in response to TGF-β1. However, the precise contribution of Tregs to experimentally induced murine lung fibrosis remains unclear. We sought to better understand the role of Tregs in this context. Using a model of fibrosis caused by lung specific, doxycycline inducible overexpression of the bioactive form of the human TGF-β1 gene we find that Tregs accumulate in the lung parenchyma within 5 days of transgene activation and that this enhancement persists to at least 14 days. Anti-CD25 Antibody mediated depletion of Tregs causes increased accumulation of soluble collagen and of intrapulmonary CD45+Col Iα1 fibrocytes. These effects are accompanied by enhanced local concentrations of the classical inflammatory mediators CD40L, TNF-α, and IL-1α, along with the neuroimmune molecule fibroblast growth factor 9 (FGF-9, also known as “glial activating factor”). FGF-9 expression localizes to parenchymal cells and alveolar macrophages in this model and antibody mediated neutralization of FGF-9 results in attenuated detection of intrapulmonary collagen and fibrocytes without affecting Treg quantities. These data indicate that CD4+CD25+FoxP3+ Tregs attenuate TGF-β1 induced lung fibrosis and fibrocyte accumulation in part via suppression of FGF-9.

Genetic architecture of human fibrotic diseases: disease risk and disease progression

Genetic studies of human diseases have identified multiple genetic risk loci for various fibrotic diseases. This has provided insights into the myriad of biological pathways potentially involved in disease pathogenesis. These discoveries suggest that alterations in immune responses, barrier function, metabolism and telomerase activity may be implicated in the genetic risks for fibrotic diseases. In addition to genetic disease-risks, the identification of genetic disease-modifiers associated with disease complications, severity or prognosis provides crucial insights into the biological processes implicated in disease progression. Understanding the biological processes driving disease progression may be critical to delineate more effective strategies for therapeutic interventions. This review provides an overview of current knowledge and gaps regarding genetic disease-risks and genetic disease-modifiers in human fibrotic diseases.

Regulation and Relevance of Myofibroblast Responses in Idiopathic Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a chronic, progressive, incurable lung disease of unknown etiology with only limited treatment options. Current paradigms of disease pathogenesis feature recurrent or prolonged epithelial injury and an ensuing inflammatory response that culminates in the appearance of activated myofibroblasts. These cells are believed central to the excessive deposition of extracellular matrix that eventually obliterates the alveolar space to cause respiratory failure. Because the factors driving the accumulation of myofibroblasts remain poorly understood, effective therapies remain elusive. This review focuses on recent understanding of myofibroblasts including their seemingly uncontrolled proliferation and survival, their controversial origin in pathological IPF tissues, and the local biochemical and biomechanical matrix factors that drive their behavior. In addition, novel antifibrotics under development for the treatment of lung disease will be discussed. As our understanding of fibroblast and myofibroblast biology regulation expands, these cells may prove to be effective therapeutic targets.

Diabetic nephropathy: the role of inflammation in fibroblast activation and kidney fibrosis

Kidney disease associated with diabetes mellitus is a major health problem worldwide. Although established therapeutic strategies, such as appropriate blood glucose control, blood pressure control with renin-angiotensin system blockade, and lipid lowering with statins, are used to treat diabetes, the contribution of diabetic end-stage kidney disease to the total number of cases requiring hemodialysis has increased tremendously in the past two decades. Once renal function starts declining, it can result in a higher frequency of renal and extra-renal events, including cardiovascular events. Therefore, slowing renal function decline is one of the main areas of focus in diabetic nephropathy research, and novel strategies are urgently needed to prevent diabetic kidney disease progression. Regardless of the type of injury and etiology, kidney fibrosis is the commonly the final outcome of progressive kidney diseases, and it results in significant destruction of normal kidney structure and accompanying functional deterioration. Kidney fibrosis is caused by prolonged injury and dysregulation of the normal wound-healing process in association with excess extracellular matrix deposition. Kidney fibroblasts play an important role in the fibrotic process, but the origin of the fibroblasts remains elusive. In addition to the activation of residential fibroblasts, other important sources of fibroblasts have been proposed, such as pericytes, fibrocytes, and fibroblasts originating from epithelial-to-mesenchymal and endothelial-to-mesenchymal transition. Inflammatory cells and cytokines play a vital role In the process of fibroblast activation. In this review, we will analyze the contribution of inflammation to the process of tissue fibrosis, the type of fibroblast activation and the therapeutic strategies targeting the inflammatory pathways in an effort to slow the progression of diabetic kidney disease.

Cellular mechanisms of tissue fibrosis. 1. Common and organ-specific mechanisms associated with tissue fibrosis

Fibrosis is a pathological scarring process that leads to destruction of organ architecture and impairment of organ function. Chronic loss of organ function in most organs, including bone marrow, heart, intestine, kidney, liver, lung, and skin, is associated with fibrosis, contributing to an estimated one third of natural deaths worldwide. Effective therapies to prevent or to even reverse existing fibrotic lesions are not yet available in any organ. There is hope that an understanding of common fibrosis pathways will lead to development of antifibrotic therapies that are effective in all of these tissues in the future. Here we review common and organ-specific pathways of tissue fibrosis.